Timing: Fixes timer when app get into background (#24649)
Timing: Fixes timer when app get into background (#24649)

Summary:
Related #23674, in that PR, we imported background timer support, but it's not sufficient, I think the reason that works is because it enable the `Background Modes` and do some background tasks, for the users who don't enable it, timer would pause immediately before goes into background.

To fix it, we can mark a background task when goes into background, it can keep app active for minutes, try best to support timing when in background.

cc. cpojer .

## Changelog

[iOS] [Fixed] - Timing: Fixes timer when app get into background
Pull Request resolved: https://github.com/facebook/react-native/pull/24649

Differential Revision: D15554451

Pulled By: cpojer

fbshipit-source-id: a33f7afe6b63d1a4fefcb7098459aee0c09145da

arthuralee/react-native,facebook/react-native,myntra/react-native,myntra/react-native,facebook/react-native,javache/react-native,hammerandchisel/react-native,hammerandchisel/react-native,exponent/react-native,janicduplessis/react-native,pandiaraj44/react-native,javache/react-native,pandiaraj44/react-native,myntra/react-native,facebook/react-native,hammerandchisel/react-native,exponent/react-native,javache/react-native,javache/react-native,facebook/react-native,javache/react-native,exponentjs/react-native,hoangpham95/react-native,exponent/react-native,hoangpham95/react-native,janicduplessis/react-native,javache/react-native,hoangpham95/react-native,hammerandchisel/react-native,hoangpham95/react-native,myntra/react-native,hammerandchisel/react-native,janicduplessis/react-native,facebook/react-native,facebook/react-native,arthuralee/react-native,pandiaraj44/react-native,arthuralee/react-native,janicduplessis/react-native,exponentjs/react-native,myntra/react-native,myntra/react-native,myntra/react-native,exponentjs/react-native,janicduplessis/react-native,exponentjs/react-native,exponentjs/react-native,javache/react-native,arthuralee/react-native,myntra/react-native,exponent/react-native,facebook/react-native,pandiaraj44/react-native,hammerandchisel/react-native,pandiaraj44/react-native,exponent/react-native,hoangpham95/react-native,exponentjs/react-native,pandiaraj44/react-native,hoangpham95/react-native,hammerandchisel/react-native,janicduplessis/react-native,pandiaraj44/react-native,exponent/react-native,janicduplessis/react-native,pandiaraj44/react-native,javache/react-native,exponent/react-native,hammerandchisel/react-native,myntra/react-native,javache/react-native,exponentjs/react-native,arthuralee/react-native,hoangpham95/react-native,janicduplessis/react-native,exponent/react-native,exponentjs/react-native,facebook/react-native,facebook/react-native,hoangpham95/react-native